The present invention relates to a storage controller and a control method of the storage controller.
A storage controller reads or writes data from or in a hard disk drive in accordance with a data input/output request transmitted from an information processor. Moreover, the storage controller is provided with a cache memory for storing the data to be read from or written in the hard disk drive and thereby, a response to the data input/output request from the information processor is accelerated.
JP-A-11-203201 is a document relating to the present invention.
The cache memory frequently uses a volatile memory such as an SDRAM (Synchronous Dynamic Random Access Memory). In this case, however, when supply of power to the cache memory is stopped, the data stored in the cache memory disappears. Therefore, it is necessary to prepare a spare power unit such as a battery for a storage controller so that the data stored in the cache memory does not disappear even when supply of power to the cache memory is stopped due to power failure.
Therefore, it is considered to use a nonvolatile memory such as a flash EEPROM (Electrically Erasable and Programmable Read Only Memory) for a cache memory. In this case, however, though the data stored in the cache memory does not disappear even if supply of power to the cache memory is stopped, the data is stored in the cache memory in the state at that time even if the cache memory is removed from a storage controller. Therefore, it is necessary to prevent the data stored in the cache memory from leaking.